The present invention relates to a catheter guide wire used in inserting a catheter into a blood vessel, ureter, trachea or the like.
As conventional catheter guide wires, those disclosed in Japanese Patent Application Publication No. 2-24549 and Japanese Patent Application Publication No. 2-24550 are known, which will be briefly explained in the following.
That is, the above-mentioned catheter guide wire is formed of an identical material and comprises a body portion, a tip end portion having a cross section smaller than that of the body portion, and a connect portion for connecting the body portion and the tip portion. Each portion (body portion, tip end portion and connect portion) has a transformation point and the property of super-elasticity (See for definition of the term JIS H7001 published by Japanese Standard Association).
Accordingly, the above-mentioned catheter guide wire can have flexibility (softness) by super-elastically deforming via stress inducible martensite transformation and its reverse transformation. Therefore, it is possible to insert the guide wired into a blood vessel or the like in conformance with the shape of the blood vessel or the like.
Though the prior art enables the catheter guide wire to be inserted in conformance with the shape of a blood vessel or the like because each portion (body portion, tip end portion and connect portion) has the respective flexibility, since the rigidity of the body portion is not sufficient, the power of pressing the catheter guide wire is not sufficiently transmitted from the body portion side to the connect portion side, which leads to the problem of poor insertion operability of the catheter guide wire.
The present invention was made in response to such a requirement. Therefore, it is an object of the invention to provide a catheter guide wire and a method of producing a catheter guide wire which eliminate the above-mentioned problem and drawback.
In order to achieve the above object, a catheter guide wire according to the first aspect of the present invention is a catheter guide wire which comprises a body portion, a tip end portion and a connect portion for connecting the body portion and the tip end portion, and is formed seamlessly of an identical material, the catheter wire being featured in that it consists of a part having a transformation point and a part not having a transformation point, and that the body portion is the part not having a transformation point.
According to the specified feature of the first aspect of the present invention, it is possible to super-elastically deform the part having a transformation point via stress inducible martensite transformation and its reverse transformation, so that it has flexibility (softness). On the other hand, the part not having a transformation point, particularly, the body portion will not super-elastically deform, so that it will not be excessively flexible and has appropriate rigidity.
Therefore, the power of pressing the catheter guide wire is sufficiently transmitted from the body portion side to the connect portion side, which improves the insertion operability of the catheter guide wire.
According to the specified feature of the first aspect of the present invention, a catheter guide wire according to the second aspect of the present invention is characterized in that, the body portion and the tip end portion are the part not having a transformation point, and the connect portion is the part having a transformation point.
According to the specified feature of the second aspect of the present invention, since the connect portion is the part having a transformation point and thus can super-elastically deform via stress inducible martensite transformation and its reverse transformation, it has flexibility. Furthermore, since the body portion is the part not having a transformation point, it will not super-elastically deform, and hence it has appropriate rigidity without becoming excessively flexible. Furthermore, since the tip end portion is the part not having a transformation point, it will not super-elastically deform, but can be plastically deformed.
Therefore, in addition to the effect of the first aspect, it is possible to plastically deform the tip end portion, which enables a physician to shape the tip end portion into an appropriate shape in accordance with the situation during operation.
According to the specified features of the first aspect and the second aspect of the present invention, a catheter guide wire according to the third aspect of the present invention is characterized in that the material is a material based on Ni and Ti; the part not having a transformation point is a part subjected to a heat treatment at a temperature of less than 350xc2x0 C. after cold working; and the part having a transformation point is a part subjected to a heat treatment at a temperature of more than or equal to 400xc2x0 C. (preferably 400xc2x0 C. to 600xc2x0 C.) after cold working.
According to the specified feature of the third aspect of the present invention, the same operation as that of either the first aspect or the second aspect is achieved.
A catheter guide wire according to the fourth aspect of the present invention is a catheter guide wire which comprises a body portion, a tip end portion and a connect portion for connecting the body portion and the tip end portion, and is seamlessly formed of a material based on Ni and Ti, the catheter guide wire being featured in that a rigidity value of the body portion is larger that of the connect portion.
In this context, the term xe2x80x9crigidity valuexe2x80x9d represents the degree of strength against bending rather than the degree of strength against tensile.
According to the specified feature of the fourth aspect of the present invention, since the rigidity value of the body portion is larger than that of the connect portion, the body portion will not become excessively flexible but has appropriate rigidity.
Therefore, the power of pressing the catheter guide wire is sufficiently transmitted to the connect portion side from the body portion side, which improves the insertion operability of the catheter guide wire.
According to the specified feature of the fourth aspect of the present invention, the catheter guide wire according to the fifth aspect of the present invention is characterized in that the body portion has a rigidity value of 5,500 to 7,000 Kg/mm2, and the connect portion has a rigidity value of 3,500 to 5,000 Kg/mm2.
Besides the specified feature of the fourth aspect of the present invention, the catheter guide wire according to the sixth aspect of the present invention is characterized in that the body portion has a rigidity value of 6,500 Kg/mm2 or more, and the connect portion has a rigidity value of 5,000 to 6,000 Kg/mm2.
According to the specified features of the fifth and sixth aspects of the invention, the connect portion has flexibility, while the body portion has appropriate rigidity without becoming excessively flexible.
The seventh aspect of the present invention is a method of producing a catheter guide wire which comprises a body portion, a tip end portion and a connect portion for connecting the body portion and the tip end portion, and is seamlessly formed of a material based on Ni and Ti and subjected to a cold working, the method comprising the steps of: subjecting the body portion and the tip end portion to a heat treatment at a temperature of less than 350xc2x0 C., and subjecting the connect portion to a heat treatment at a temperature of 400xc2x0 C. or more (preferably 400xc2x0 C. to 600xc2x0 C.).
According to the specified feature of the seventh aspect of the present invention, the fact that a transformation point will not occur when the material is subjected to a heat treatment at a temperature of less than 350xc2x0 C. and that a transformation point will occur when the material is subjected to a heat treatment at a temperature of 400xc2x0 C. or more (preferably 400xc2x0 C. to 600xc2x0 C.) has been experimentally shown. Also the fact that the rigidity value will become large when the material is subjected to a heat treatment at a temperature of less than 350xc2x0 C. and that super-elastic deformation will occur when the material is subjected to a heat treatment at a temperature of 400xc2x0 C. or more (preferably 400xc2x0 C. to 600xc2x0 C.) has been experimentally shown.
Therefore, the body portion is the part not having a transformation point, so that it will not super-elastically deform and hence has appropriate rigidity without becoming excessively flexible. Similarly, the tip end portion is the part not having a transformation point, so that it will not super-elastically deform and can be plastically deformed. Furthermore, the connect portion is the part having a transformation point, so that it can super-elastically deform via stress inducible martensite transformation and its reverse transformation, and has flexibility.
According to the above-mentioned operation, the power of pressing the catheter guide wire is sufficiently transmitted to the connect portion side from the body portion side, which leads an effect of improving the insertion operability of the catheter guide wire.
Furthermore, since it is possible to plastically deform the tip end portion, a physician can shape the tip end portion into an appropriate shape in accordance with the situation during operation.
According to the specified feature of the seventh aspect of the present invention, the eighth aspect of the present invention is characterized in that working rate of the cool working is 50% or more.
According to the specified feature of the eighth aspect of the present invention, it has been experimentally shown that when the working rate is 50% or more, the rigidity value of the body portion is significantly larger than that of the connect portion. Therefore, the rigidity of the body portion is further increased compared to the connect portion.
Consequently, the insertion operability of the catheter guide wire is further improved.
The ninth aspect of the present invention is a method of producing a catheter guide wire which comprises a body portion, a tip end portion and a connect portion for connecting the body portion and the tip end portion, and is seamlessly formed of a material based on Ni and Ti and subjected to a cold working, the method comprising the steps of: subjecting the body portion, the tip end portion and the connect portion to a heat treatment at a temperature of less than 300xc2x0 C., and after that step subjecting only the connect portion to a heat treatment at a temperature of 300xc2x0 C. to 350xc2x0 C.
According to the specified feature of the ninth aspect of the present invention, by subjecting the core wire to plural times of heat treatments, the pushability and operability are further improved. That is, it is possible to realize a catheter guide wire in which the connect portion has higher rigidity rather than super-elasticity, while the connect portion being more flexible than the body portion and maintaining deformation resistance (resistant to permanent deformation).